Generally, the mmWave standard calls for a carrier frequency of 60 GHz and a channel bandwidth of 0.5˜2.5 GHz. Therefore, the mmWave standard calls for a carrier frequency and a channel bandwidth considerably greater than those of the conventional IEEE 802.11 series standard. If a radio frequency signal having a wavelength in the millimeter range is used, it is possible to provide a considerably high data rate on the order of several gigabits (Gbps). It is also possible to implement this using a single chip including an antenna having a size of 1.5 mm or less.
Because the attenuation ratio of air is very high, it is advantageous to reduce inter-station interference.
Likewise in the case of mmWave transmissions, the reaching (i.e., maximum) distance of a beam is also decreased due to high attenuation ratio. Therefore, it is particularly difficult to transmit a signal omni-directionally. In order to solve this problem, a beam needs to be sharpened. In so doing, the beam is locally delivered only (i.e., is limited to a relatively small coverage area).
In a Piconet using mmWave transmissions, a coordinator periodically transmits a beacon. The beacon generally has the structure shown in FIG. 1 in association with the medium access control (MAC) layer. As shown, the beacon includes a MAC control header, an information elements (IE) field, a parity check sequence and the like.
When a beacon is configured in accordance with current network standards, information elements are added. Various kinds of information elements exist according to the network standard. If a plurality of information elements are added to a beacon, the length of the beacon may increase significantly, thus resulting in excessive overhead.
A schedule information element (IE) is generally included in a beacon. As the name suggests, a schedule information element carries scheduling information, such as the information shown in Table 1.
TABLE 1TableItemDescriptionIE IndexIdentifying whether a present IE is a schedule IELengthLength of whole IESchedule Block 1Having schedule information with DEV 1Schedule Block 2Having schedule information with DEV 2. . .. . .Schedule Block nHaving schedule information with DEV n
As shown, the beacon may include schedule information associated with many wireless devices (DEV1, . . . , DEVn) existing in the piconet. However, it is not necessary for one device to receive information relating to another device.